CN115682952B - Geometric quantity precise measurement device and method based on spectrum confocal principle - Google Patents
Geometric quantity precise measurement device and method based on spectrum confocal principle Download PDFInfo
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Abstract
The invention discloses a geometrical quantity precise measurement device and a geometrical quantity precise measurement method based on a spectral confocal principle. The invention comprises a dual-mode measuring head, a wide-spectrum light source, an optical fiber light path, a spectrum detection module and a signal processing module. The dual-mode measuring head realizes two measuring modes of non-contact type and contact type by dividing a light path of spectrum confocal into two parts, wherein one part is used for non-contact type distance measurement and the other part is used for precisely measuring the contact state of the contact type probe. The fixed side of the contact probe is provided with a flat end face, the contact force of the probe changes the gesture and the position of the flat end face, and the spectrum detection module measures and calculates the stress position, the stress size and the stress direction of the contact probe by utilizing the spectrum confocal distance measurement principle. When the stress data is larger than the set threshold, the signal processing module outputs a trigger signal to the outside for controlling the data acquisition device to sample. The invention can realize high-precision measurement of geometric quantities such as plane angle, shape and position error, surface roughness and the like.
Description
Technical Field
The invention relates to a precise detection technology, in particular to a geometric quantity precise measurement device and method based on a spectral confocal principle.
Background
The spectral confocal displacement measurement technology is a high-precision non-contact displacement measurement technology based on the spectral confocal principle, and is proposed by the STIL company in 1995 at the earliest, and the basic principle is as follows: the white light source (usually LED light source) is transmitted to the dispersion lens in the form of optical fiber-optical fiber coupler-optical fiber, which is equivalent to forming a confocal aperture, the light of complex color is collimated by the dispersion lens and then focused, axial dispersion occurs on the main optical axis, and a series of continuous focusing points are formed, namely, monochromatic light with different wavelengths is focused on different positions on the main optical axis. When the measured object is at a certain distance from the lens, only light with specific wavelength is focused on the measured object, and the measured object is in a confocal state, the energy reflected back to the lens is concentrated in distribution, and the received luminous flux is large; the light with other wavelengths is not focused on the measured object and is in an out-of-focus state, the light distribution range of the reflected light back to the lens is far larger than the diameter of the fiber core, and the received light flux is small. The obtained reflected light is a continuous spectrum with a single peak value, and the spectrum is sent to a spectrometer for decoding to obtain the corresponding wavelength at the position with the maximum light intensity, so that the displacement information of the measured object can be obtained. In an ideal case, the wavelength of light is linear with its focal position.
Currently, the spectral confocal displacement measurement sensor has mature commercial products, mainly foreign manufacturers have STIL, precitec, micro-Epsilon, keyence and the like, and mainly domestic manufacturers have ThinkFocus, stereo instruments, halbersen, visual-creating intelligence and the like. A wide variety of sensors were developed according to different measurement requirements, with the highest resolution being up to the nanometer level, the highest measurement speed being up to 70kHz, and with the smallest outer diameter of 4mm of the axial, radial probe to meet the measurement requirements in the aperture, slit.
In particular measurement applications, the above-mentioned techniques and products require that the surface of the object to be measured be smooth and have a good roughness level, and that the main optical axis of the dispersive lens be as perpendicular as possible to the surface of the object to be measured. The single-mode spectral confocal displacement sensor is limited by the caliber and the measuring range of a dispersion lens, and a measuring blind area is often formed when a complex structural member is measured. These situations limit the application of spectral confocal displacement measurement techniques.
Disclosure of Invention
The spectral confocal displacement measurement technology is a mature high-precision non-contact displacement measurement technology, but the measurement technology needs to have good surface roughness of an object to be measured, and the main optical axis of the dispersion lens is required to be perpendicular to the surface of the object to be measured as much as possible. The above situation makes the application scenario thereof greatly limited, and especially cannot satisfy the measurement of complex components. The invention aims to provide a geometric quantity precise measurement technology based on a spectral confocal principle and having two working modes, and the invention provides a dual-mode measuring head which realizes two measurement modes, namely a non-contact type measuring mode and a contact type measuring mode by dividing a spectral confocal optical path into two parts, wherein one part is used for non-contact type distance measurement and the other part is used for precisely measuring the contact state of a contact type probe. The contact measurement mode does not require the surface of the object to be measured to have a good roughness level, nor does the axis of the contact probe need to be perpendicular to the surface of the object to be measured. By means of probes of different lengths, the working distance of the measuring device can be prolonged. Therefore, the two working modes are matched with each other, and the dead zone of the complex structural member during measurement can be effectively reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a geometrical quantity precise measurement device based on a spectrum confocal principle comprises a dual-mode measuring head, a wide-spectrum light source, a pinhole component, an optical fiber light path, a spectrum detection module and a signal processing module.
The dual-mode measuring head consists of a dispersion lens group, a light splitting module, a contact probe, a probe base and a shell; the light splitting module divides the light path into two parts, wherein one part is used for non-contact distance measurement and the other part is used for accurately measuring the contact state between the contact probe and the workpiece; the wide spectrum light source generates white light, is coupled into the dispersion mirror group through the optical fiber optical path, and is dispersed in two directions through the light splitting module; the pinhole member includes a plurality of pinholes that enable light of a specific wavelength irradiated and focused on a measurement object to return to the pinholes after being reflected, thereby constituting spectral confocal; the spectrum detection module is used for detecting spectrum distribution information of the reflected light; the signal processing module is used for decoupling the spectrum distribution information of the two paths of reflected light and obtaining distance data of non-contact distance measurement and the contact state of the contact probe; the reference center point of the light splitting module, the measuring site of the non-contact distance measurement and the contact site of the contact probe form a triangle with known side length.
Furthermore, the light splitting module is provided with an independent shell, and a detachable fixed connection mode is adopted between the light splitting module and the shell, and the preferred connection mode is threaded connection; the light splitting surface of the light splitting module forms an angle with the optical axis of the dispersing lens group, and the angle is preferably 135 degrees.
Further, the contact probe comprises a measuring rod and a ball head; the measuring rod and the ball head are made of materials with high rigidity, the preferable measuring rod materials comprise ceramics, tungsten carbide and the like, and the preferable ball head materials comprise ruby, silicon nitride, zirconium oxide, tungsten carbide and the like; the measuring rod comprises a straight shoulder measuring rod and a conical measuring rod, and the preferred configuration is the conical measuring rod; the ball head is positioned at the measuring end part of the measuring rod, and the fixed end part of the measuring rod is connected with the probe base; the probe base and the contact probe adopt a detachable fixing mode; the probe base has a flat end surface, the roughness Ra is better than 0.5 micron, and the flatness is better than 0.5 wavelength; the position of the flat end surface is at the working distance of the spectral confocal, and the error is less than one tenth of the range of the spectral confocal distance measurement; the probe base is connected with the shell of the light splitting module, and when the contact probe contacts a measuring object, micro movement can be generated between the probe base and the shell of the light splitting module.
Further, the optical fiber path comprises a first optical fiber, a second optical fiber, a third optical fiber and an optical fiber coupler; the optical fiber coupler is provided with three ports, namely an optical inlet, an optical outlet, a coupling port and the like; one end of the first optical fiber is connected to the wide spectrum light source, and the other end of the first optical fiber is connected to the light inlet of the optical fiber coupler; one end of the second optical fiber is connected to the coupling port of the optical fiber coupler, and the other end of the second optical fiber is connected to the dual-mode measuring head; one end of the third optical fiber is connected to the light outlet of the optical fiber coupler, and the other end of the third optical fiber is connected to the spectrum detection module; the composite light generated by the wide-spectrum light source enters the dual-mode measuring head through the first optical fiber, the optical fiber coupler and the second optical fiber in sequence, and irradiates the light splitting module through the dispersion lens group; the first optical fiber, the second optical fiber, the third optical fiber and the optical fiber coupler form an optical fiber light path unit, and the end part of the second optical fiber is the pinhole.
Further, the optical fiber path includes a plurality of the optical fiber path units, wherein a plurality of the second optical fibers constitute the pinhole member; the pinhole member having the pinholes in the same number as the second optical fibers; the pinholes are distributed at different positions of an image space focal plane of the dispersive lens group; light coupled into the second optical fiber is emitted out through the pinhole and subjected to axial dispersion after passing through the dispersion mirror group, and light with different wavelengths is focused at different axial positions; light emitted by different pinholes and passing through the dispersive lens group is focused at different object focal plane positions; three or more of the pinholes are present, and any three of the pinholes are not collinear in spatial distribution.
Further, after the light emitted by different pinholes passes through the dispersion mirror group and the light splitting module, the light with specific wavelength is focused to different positions of the flat end face of the probe base; after being reflected by the flat end face, the light with the specific wavelength sequentially passes through the light splitting module, the dispersion lens group, the pinhole, the second optical fiber, the optical fiber coupler and the third optical fiber and finally enters the spectrum detection module; and the spectrum detection module acquires the collected spectrum distribution information of the light reflected by the flat end surface and obtains a distance value corresponding to the focusing position.
Further, a measurement space coordinate system is established by taking the mechanical structure of the dual-mode measuring head as a reference; taking the optical axis direction of the dispersive lens group as the z direction of the measurement space coordinate system; taking an object focal plane of monochromatic laser with a specific wavelength as a zero plane in the z direction of the measurement space coordinate system, wherein the specific wavelength is preferably 500nm; the intersection line of the light splitting surface of the light splitting module and the zero plane is used as the y direction of the measurement space coordinate system, and the direction perpendicular to the y direction of the zero plane is used as the x direction of the measurement space coordinate system; the intersection point of the optical axis of the dispersive lens group and the zero plane is the geometric zero point of the measurement space coordinate system, and the direction away from the dispersive lens group is the positive direction of the z-axis;
Further, the focusing point of the pinhole corresponding to the flat end surface is marked as P 1 ，P 2 ，…，P n ，P i The sitting corresponding to point (i=1, 2, …, n) is marked as (x) i ，y i ，z i ) The space equation of the flat end surface is expressed as xcosα+ycosβ+zcosγ=p, and then
Wherein alpha, beta and gamma are respectively included angles between the normal direction of the flat end surface and x, y and z directions of the measurement space coordinate system, and p is the distance from the origin of coordinates of the measurement space coordinate system to the flat end surface;
the distance between the center point of the flat end surface and the center of the ball head is L, the center coordinates of the ball head are (lcos α -M cos α, lcos β -M cos β, lcos γ -M cos γ+m- Δp), where m=n+Δp, M represents the distance between a specific point on the axis of the contact probe and the origin of the measurement space coordinate system, the space coordinates of the specific point are (0, M), N represents the distance between the center point of the flat end surface and the specific point when the contact probe does not contact any measurement object, Δp represents the offset correction amount of the center point of the flat end surface in the axis direction of the contact probe due to the contact force, Δp can be calculated iteratively according to the space equation of the flat end surface, and the initial value is Δp=m cos γ -N-p; and calculating the stress balance of the contact probe according to the connection mode between the probe base and the shell of the light splitting module by utilizing the delta p, alpha, beta, gamma and other information. Thirdly, deducing the contact position and the contact force direction of the ball head by utilizing the stress balance of the contact probe, and obtaining an accurate delta p value by iterative calculation, and realizing ball head compensation by the delta p value and the radius of the ball head; and constructing a space straight line by using the specific point coordinates on the axis of the contact probe and the spherical center coordinates of the ball head, and describing the gesture of the measuring rod by using the vector of the obtained space straight line, thereby realizing the calibration of the gesture of the measuring rod described by the angles of alpha, beta, gamma and the like.
The geometrical quantity precise measurement method based on the spectral confocal principle can detect the critical contact state position through the contact probe, and the detection comprises the following steps:
step 1, along a specific direction L i (i=x, y, z) performing protection movement to the target to be detected, and when the condition |alpha-90|+|beta-90|+|gamma|is not less than T is satisfied d Or Δp.gtoreq.T p When the movement is stopped, the current L is recorded i Coordinate position l corresponding to (i=x, y, z) u-i ；
Step 2, along a specific direction L i Reverse low-speed movement of (i=x, y, z), real-time recording and L i Δp, |α -90|+|β -90|+|γ| corresponding to (i=x, y, z) coordinate positions form two corresponding curves S l-Δp 、S l-αβγ ；
Step 3, for the S l-Δp Curve sum S l-αβγ Performing wavelet transformation on the curve, and calculating to obtain L corresponding to the critical contact state of the ball head and the target to be detected based on wavelet and signal correlation criteria i (i=x, y, z) axis coordinate position l c-i 。
Furthermore, the geometrical quantity precise measurement method based on the spectral confocal principle can measure the distance in two directions at the same time, and specifically comprises the following steps:
step 1, defining two surfaces to be measured as Pn according to the measurement space coordinate system x And Pn z Adjusting the gesture of the dual-mode measuring head to ensure that the x direction of the measurement space coordinate system and the surface Pn to be measured x The angle between the normals of (a) is smaller than the maximum allowable angle for the non-contact distance measurement;
step 2, along the x-axis of the measurement space coordinate system, the surface Pn to be measured x Performing protection movement, analyzing the spectrum obtained by the spectrum detection module, stopping movement when the amplitude corresponding to the 650nm wavelength exceeds a set threshold value, and recording the x-axis coordinate position l nc-x ；
Step (a)3. The surface Pn to be measured along the z-axis of the measurement space coordinate system z Performing protection movement to obtain the ball head and the surface Pn to be tested z Z-axis coordinate position l corresponding to critical contact state of (2) c-z ；
Step 4, moving to a z-axis coordinate position l along the z-axis of the measurement space coordinate system c-z Analyzing the spectrum obtained by the spectrum detection module, wherein the obtained spectrum has two spectrum peaks, one peak is near 650nm wavelength, so as to calculate and obtain the p value in the space equation of the flat end face, and the other peak corresponds to the measured value n of the non-contact distance measurement, and the surface Pn to be measured is obtained x Distance measurement value l nc-x +n, the surface Pn to be measured y Distance measurement value l c-z +p+L。
Further, the geometrical quantity precise measurement method based on the spectral confocal principle can precisely measure the plane angle, and the plane angle precise measurement method comprises the following steps:
Step 1, selecting a contact probe with proper length according to the approximate range of a plane angle to be measured, wherein the selection principle is that the relative error between an included angle ACB formed by a measurement site A of the non-contact distance measurement, a contact site B of the contact probe and a reference center point C of the light splitting module and the plane angle is less than 5%;
step 2, carrying out protection movement along the x-axis direction to the plane to be tested, when |alpha-90|+|beta-90|+|gamma|is not less than T d Or Δp.gtoreq.T p When the movement is stopped, the current x-axis coordinate position x is recorded u And the measured value p of the non-contact distance measurement nc-u Simultaneously recording the spatial equation x cosα+y cosβ+z cosγ=p for the flat end face;
step 3, reversely moving along the x-axis at a low speed, recording deltap, |alpha-90|+|beta-90|+|gamma| corresponding to the x-axis coordinate position and the measured value of the non-contact distance measurement in real time, and forming three corresponding curves S x-Δp 、S x-αβγ 、S x-pnc ；
Step 4, for the S x-Δp Curve sum S x-αβ The gamma curve is subjected to wavelet transformation, and is calculated based on wavelet and signal correlation criteriaAn x-axis coordinate position x corresponding to the critical contact state of the ball head and the plane to be measured c ；
Step 5, finding x c At S x-pnc A set { l } of measurements of the corresponding non-contact distance measurement in the curve pnc (i) I=1, 2, …, n }, solving a local space equation x cos phi+y cos phi+z cos omega=v of the plane to be measured by using a least square method;
step 6, utilizing L, x c -x u 、p nc-u And correcting the omega value by using the gamma value obtained in the step 2 to obtain omega from a triangle formed by the reference center point of the light splitting module, the measuring site of the non-contact distance measurement and the contact site of the contact probe s The angle value of the plane to be measured is 90-omega s +γ。
Compared with the prior art, the invention has the beneficial effects that: firstly, the light path of the spectral confocal detection is divided into two parts by utilizing the light splitting device, one part is used for non-contact distance measurement, the other part is used for accurately measuring the contact state of the contact probe, and the two provided working modes are matched with each other, so that the measurement capability of the device can be expanded; secondly, the invention is based on the spectrum confocal principle, has a plurality of independent confocal light paths, can perform multi-point distance measurement in a micro area, has error correction capability, and can improve measurement accuracy; thirdly, the contact type measurement mode provided by the invention has the functions of measuring rod posture self-calibration and ball head compensation, and is beneficial to accurate measurement of curvature abrupt change areas of complex components.
Drawings
FIG. 1 is a schematic diagram of a geometrical precision measurement device based on the spectral confocal principle according to an embodiment of the invention;
FIG. 2 is a schematic diagram of the structure and composition of a dual mode probe according to one embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating an implementation of a spectroscopic surface of a spectroscopic module according to an embodiment of the present invention;
FIG. 4 is a schematic view of two variations of the spectroscopic surface of the spectroscopic module according to the present invention;
FIG. 5 is a schematic view of a device measurement space coordinate system according to one embodiment of the invention;
FIG. 6 is a schematic diagram of the dispersion focusing of incident light through a plurality of pinholes onto a planar end surface of a contact probe in accordance with one embodiment of the present invention;
FIG. 7 is a schematic view of a reflectance spectrum of a contact probe with a planar end face having a varying attitude in accordance with an embodiment of the present invention;
FIG. 8 is a schematic diagram of a critical contact state position detection process of a contact probe according to an embodiment of the present invention;
fig. 9 is a schematic diagram of the composition of a geometrical precision measurement device based on the spectral confocal principle according to a modification of the present invention.
Detailed Description
The invention will now be described in detail with reference to the drawings and examples.
The embodiment of the invention relates to a geometrical quantity precise measurement device and a geometrical quantity precise measurement method based on a spectral confocal principle, which can be used for precise measurement of geometrical quantity. The invention provides two working modes of contact measurement and non-contact measurement, and can realize high-precision measurement of geometric quantities such as plane angle, shape and position error, surface roughness and the like. The dual-mode measuring head provided by the invention does not contain any electronic device, and can complete the measurement task under the working condition of radioactivity.
First embodiment
A first embodiment proposed according to the present invention is explained below with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of a measurement apparatus according to the present invention includes a dual-mode gauge head 100, a broad spectrum light source 200, a pinhole member 300, a fiber optic path 400, a spectrum detection module 500, and a signal processing module 600.
As shown in fig. 2, in this embodiment, the dual-mode probe 100 is composed of a dispersive lens group 101, a beam splitter module 102, a contact probe 103, a probe base 104, and a housing; the light splitting module 102 divides the light path into two parts, one part is used for non-contact distance measurement, and the other part is used for precisely measuring the contact state between the contact probe 103 and the workpiece; the broad spectrum light source 200 generates white light, which is coupled into the dispersive lens group 101 through the optical fiber path 400 and is dispersed in two directions through the light splitting module 102; the pinhole member 300 includes a plurality of pinholes that enable light of a specific wavelength irradiated and focused on a measurement object to return to the pinholes after being reflected, thereby constituting spectral confocal; the spectrum detection module 500 is configured to detect spectrum distribution information of the reflected light; the signal processing module 600 is configured to decouple the spectral distribution information of the two paths of reflected light and obtain distance data of the non-contact distance measurement and a contact state of the contact probe 103; the reference center point of the spectroscopic module 102, the measuring site of the noncontact distance measurement, and the contact site of the contact probe 103 form a triangle with known side lengths. In this embodiment, the axial direction of the contact probe 103 is the same as the optical axis direction of the dispersive lens group 101.
As shown in fig. 2, in this embodiment, the optical splitting module 102 has a separate housing 102-1, and a detachable fixed connection manner is adopted between the optical splitting module and the housing, and a preferred connection manner is a threaded connection; the beam splitting plane 102-2 of the beam splitting module 102 forms an angle with the optical axis of the dispersive lens group 101, which is preferably 135 °. The side of the housing 102-1 of the spectroscopic module 102 has a measurement window 102-3. The split reflected light is emitted from the measurement window 102-3 and then strikes the surface of the object to be measured. As shown in fig. 3, the preferable embodiment of the light splitting surface 102-2 is a planar beam splitter, and a thin film half lens with a uniform thickness is used, and a surface facing the dispersive lens group 101 is subjected to a coating process to have a semi-transparent characteristic.
Fig. 4 shows two other modifications of the light splitting surface 102-2.
Fig. 4 (a) shows an embodiment of constructing the splitting plane 102-2 by using a cube-type beam splitter, which is formed by combining two 45 ° right-angle triangular prisms 102-2A and 102-2B. The inclined surfaces of the two triangular prisms are subjected to film plating treatment to form semi-permeable surfaces, and the incident light beam is divided into two parts at the inclined surfaces.
Fig. 4 (b) shows an embodiment in which the light-splitting surface 102-2 is constructed by a metal mirror having a 45 ° reflecting surface, and a part of the incident light beam is reflected along the mirror surface normal and emitted through the measurement window 102-3. And processing 3 or more through holes on the metal reflecting mirror along the optical axis direction of the dispersion lens, wherein part of incident light beams directly pass through the through holes. In this embodiment, the reflected light used for non-contact distance measurement and for precisely measuring the contact state of the contact probe do not interfere with each other, and analysis of the reflected light spectrum is easy.
As shown in fig. 2, in the present embodiment, the contact probe 103 includes a stylus 103-1 and a ball 103-2; the measuring rod 103-1 and the ball 103-2 are made of materials with high rigidity, the preferable measuring rod materials comprise ceramics, tungsten carbide and the like, and the preferable ball materials comprise ruby, silicon nitride, zirconium oxide, tungsten carbide and the like; the configuration of the measuring rod 103-1 comprises a straight shoulder measuring rod and a conical measuring rod, and the conical measuring rod is adopted in the embodiment; the ball head 103-2 is positioned at the measuring end of the measuring rod 103-1, and the fixed end of the measuring rod 103-1 is connected with the probe base 104; a detachable fixing mode is adopted between the probe base 104 and the contact probe 103; the probe base 104 has a planar end surface 106 with a roughness Ra of better than 0.5 microns and a planarity of better than 0.5 wavelengths; the position of the flat end surface 106 is at the working distance of the spectral confocal, and the error is less than one tenth of the range of the spectral confocal distance measurement; the probe base 106 is connected with the housing 102-1 of the spectroscopic module 102 by a flexible hinge 105; when the contact probe 103 contacts with a measurement object, the flexible hinge 105 deforms, so as to drive the flat end surface 106 to slightly deflect and slightly move.
As shown in fig. 1, in the present embodiment, the optical fiber path 400 includes a first optical fiber 401, a second optical fiber 402, a third optical fiber 403, and an optical fiber coupler 404; the optical fiber coupler 404 has three ports, namely an optical inlet, an optical outlet, a coupling port and the like; one end of the first optical fiber 401 is connected to the broad spectrum light source, and the other end is connected to the light inlet of the optical fiber coupler 404; one end of the second optical fiber 402 is connected to the coupling port of the optical fiber coupler 404, and the other end is connected to the dual-mode probe 100; one end of the third optical fiber 403 is connected to the light outlet of the optical fiber coupler 404, and the other end is connected to the spectrum detection module 500; the composite light generated by the broad spectrum light source 200 enters the dual-mode probe 100 through the first optical fiber 401, the optical fiber coupler 404 and the second optical fiber 402 in sequence, and irradiates the light splitting module 102 through the dispersive lens group 101; the first optical fiber 401, the second optical fiber 402, the third optical fiber 403 and the optical fiber coupler 404 form an optical fiber optical path unit; as shown in fig. 5, the end of the second optical fiber 402 is the pinhole 402-1.
In this embodiment, the optical fiber path 400 includes a plurality of optical fiber path units, in which the second optical fibers 402 together form the pinhole member 300; the pinhole member 300 has the pinholes 402-1 in the same number as the second optical fibers 402; as shown in fig. 6, a plurality of pinholes 402-1 are distributed at different positions of the image-side focal plane of the dispersive lens group 101; light coupled into the second optical fiber 402 is emitted through the pinhole and axially dispersed after passing through the dispersing lens group 101, and light with different wavelengths is focused at different axial positions; as shown in fig. 6, the light exiting from different pinholes 402-1 and passing through the dispersive lens group 101 is focused at different object focal plane positions; there are three or more of the pinholes 402-1 and any three of the pinholes are not collinear in spatial distribution.
As shown in fig. 1 and 6, in the present embodiment, after the light emitted from the different pinholes 402-1 passes through the dispersive lens group 101 and the beam splitting module 102, the light with a specific wavelength is focused at different positions on the planar end surface 106 of the probe base 104; after being reflected by the flat end surface 106, the light with the specific wavelength sequentially passes through the light splitting module 102, the dispersive lens group 101, the pinhole 402-1, the second optical fiber 402, the optical fiber coupler 404 and the third optical fiber 403, and finally enters the spectrum detection module 500; the spectrum detection module 500 acquires the collected spectrum distribution information of the light reflected by the flat end surface 106, and obtains a distance value corresponding to the focusing position.
As shown in fig. 1, in this embodiment, a spectrum detection module 500 in the apparatus includes a first lens 501, a grating beam splitter 502, a second lens 503, and a light detector 504, where:
the first lens 501 collimates the light output from the third optical fiber 403 and makes the collimated light incident on the grating beam splitter 502 in a linear array; the grating beam splitter 502 reflects incident light according to different wavelengths and different angles, and passes through the second lens 503 to form a plurality of light beams, and finally the light beams are incident on the light detector 504; the photodetector 504 is a planar array detector, and may be a CMOS (complementary metal oxide semiconductor) or CCD (charge coupled device) image sensor.
The signal processing module 600 is composed of a digital signal processor, a logic control circuit, a light source driving and controlling circuit, an external input and output circuit, a data memory and the like. Wherein, the logic control circuit is used for controlling the exposure of the optical detector 504, and collecting the electric signal output by the optical detector 504 into a digital signal; the digital signal processor is used for processing the digital signal to obtain spectrum information and storing the data through the data memory; the light source driving and controlling circuit is used for supplying power to the wide spectrum light source 200 and controlling the brightness thereof; the external input/output circuit is used for accessing an external trigger signal and also used for outputting an external signal when the gesture and the position of the contact probe 103 exceed a defined threshold.
Furthermore, the digital signal processor, the logic control circuit, the light source driving and controlling circuit, the external input and output circuit and the data memory can be all existing mature equipment.
As shown in fig. 5, in this embodiment, a measurement space coordinate system is established with reference to the mechanical structure of the dual-mode probe 100; taking the optical axis direction of the dispersive lens group 101 as the z direction of the measurement space coordinate system; taking the object focal plane of monochromatic laser with a specific wavelength as a zero plane 102-4 in the z direction of the measurement space coordinate system, wherein the specific wavelength is preferably 500nm; an intersection line of the light splitting plane 102-2 of the light splitting module 102 and the zero plane 102-4 is taken as a y direction of the measurement space coordinate system, and a direction perpendicular to the y direction of the zero plane is taken as an x direction of the measurement space coordinate system; the intersection point of the optical axis of the dispersive lens group 101 and the zero plane 102-4 is the geometric zero point O of the measurement space coordinate system, and the direction away from the dispersive lens group 101 is the positive direction of the z-axis;
As shown in fig. 6, the focusing point of the pinhole 402-1 corresponding to the flat end surface 106 is denoted as P 1 ，P 2 ，…，P n ，P i The sitting corresponding to point (i=1, 2, …, n) is marked as (x) i ，y i ，z i ) The spatial equation of the flat end surface 106 is expressed as xcosα+ycosβ+zcosγ=p, and there is
Wherein α, β, γ are angles between the normal direction of the flat end surface 106 and x, y, z directions of the measurement space coordinate system, and p is a distance from the origin 0 of coordinates of the measurement space coordinate system to the flat end surface 106.
As shown in fig. 7 (a) and 7 (b): when the contact probe 103 is not in contact with any measuring object, the normal line of the flat end surface 106 is parallel to the optical axis of the dispersive lens group 101, and the focusing point P 1 ，P 2 ，P 3 The reflected spectrum information is respectively shown as A01, A02 and A03; when the contact probe 103 contacts with the object to be measured, the reaction force of the contact causes the measuring rod 103-1 to displace and deflect, and further drives the flat end surface 106 to slightly deflect and slightly move, so that the focusing point P is at the moment 1 ，P 2 ，P 3 The focus wavelength of (c) is changed and the spectral information reflected back is shown as a04, a05, a06, respectively. The spectral peak offsets of A01 and A04, A02 and A05, A03 and A06 can be analyzed to measure P 1 ，P 2 ，P 3 Distance information of the focus point is equal.
The distance between the center point C of the flat end surface 106 and the center of the ball 103-2 is L, and then the center coordinates of the ball 103-2 are (lcos α -mcos α, lcos β -mcos β, lcos γ -mcos γ+m- Δp), where m=n+Δp, M represents the distance between a specific point Q on the axis of the contact probe 103 and the origin 0 of the measurement space coordinate system, the space coordinates of the specific point Q are (0, M), N represents the distance between the center point of the flat end surface 106 and the specific point Q when the contact probe 103 does not contact any measurement object, Δp represents the offset correction amount of the center point C of the flat end surface 106 along the axis direction of the contact probe 103 due to the contact force, Δp can be calculated by the space equation according to the flat end surface 106, and the initial value thereof is Δp=m cos γ -N-p; according to the hinge connection manner between the probe base 104 and the housing 102-1 of the light splitting module 102, the stress balance of the contact probe 103 is calculated by using the Δp, α, β, γ and other information, and the contact position and the contact force direction of the ball 103-2 are deduced.
Depending on the geometric quantity precise measurement device based on the spectral confocal principle provided in the present embodiment, a geometric quantity precise measurement method based on the spectral confocal principle can detect the critical contact state position by the contact probe 103, as shown in fig. 8, the detection includes the following steps:
Step 1, along a specific direction L i (i=x, y, z) when the condition |α -90|+|β -90|+|γ|Σ Σ is satisfied d Or Δp.gtoreq.T p When the movement is stopped, the current L is recorded i Coordinate position l corresponding to (i=x, y, z) u-i ；
In a specific direction L k Performing protection movement on a target to be detected, wherein k=x, y and z; when meeting the condition |alpha-90|+|beta-90|+|gamma|not less than T d Or Δp.gtoreq.T p When the movement is stopped, the current L is recorded k Corresponding coordinate position l u-k ；
Step 2, along a specific direction L k Reverse low-speed movement of (1), real-time recording and L k Δp, |alpha-90|+|beta-90|+|gamma| corresponding to the coordinate positions, and two corresponding curves S are formed l-Δp 、S l-αβγ ；
Step 3, for the S l-Δp Curve sum S l-αβγ Performing wavelet transformation on the curve, and calculating to obtain L corresponding to the critical contact state of the ball 103-2 and the target to be detected based on wavelet and signal correlation criteria k Axis coordinate position l c-k 。
In this embodiment, a geometric quantity precise measurement method based on a spectral confocal principle can measure distances in two directions simultaneously, and specifically includes the following steps:
step 1, defining two surfaces to be measured as Pn according to the measurement space coordinate system x And Pn z Adjusting the posture of the dual-mode probe 100 to enable the x direction of the measurement space coordinate system and the surface Pn to be measured x The angle between the normals of (a) is smaller than the maximum allowable angle for the non-contact distance measurement;
step 2, along the x-axis of the measurement space coordinate system, the surface Pn to be measured x Performing protection movement, analyzing the spectrum obtained by the spectrum detection module 500, stopping movement when the amplitude corresponding to the 650nm wavelength exceeds a set threshold value, and recording the x-axis coordinate position l nc-x ；
Step 3, along the z-axis of the measurement space coordinate system, the surface Pn to be measured z Performing a protection movement to obtain the ball 103-2 and the surface Pn to be tested z Z-axis coordinate position l corresponding to critical contact state of (2) c-z ；
Step 4, moving to a z-axis coordinate position l along the z-axis of the measurement space coordinate system c-z Analyzing the spectrum obtained by the spectrum detection module 500, wherein the obtained spectrum has two spectral peaks, one peak is near 650nm wavelength, so as to calculate the p value in the space equation of the flat end surface 106, and the other peak corresponds to the measured value n of the non-contact distance measurement, and the surface Pn to be measured is obtained x Distance measurement value l nc-x +n, the surface Pn to be measured y Distance measurement value l c-z +p+L。
In this embodiment, a geometrical quantity precise measurement method based on a spectral confocal principle can precisely measure a plane angle, and the plane angle precise measurement method includes the following steps:
Step 1, selecting a contact probe with proper length according to the approximate range of the plane angle to be measured, wherein the selection principle is that the relative error of an included angle ACB formed by a measurement site A of the non-contact distance measurement, a contact site B of the contact probe 103 and a reference center point C of the light splitting module 102 and the plane angle is less than 5%;
step 2, carrying out protection movement along the x-axis direction to the plane to be tested, when |alpha-90|+|beta-90|+|gamma|is not less than T d Or Δp.gtoreq.T p When the movement is stopped, the current x-axis coordinate position x is recorded u And the measured value p of the non-contact distance measurement nc-u Simultaneously recording the spatial equation xcoα+ycoβ+zcosγ=p for the planar end surface 106;
step 3, reversely moving along the x-axis at a low speed, recording deltap, |alpha-90|+|beta-90|+|gamma| corresponding to the x-axis coordinate position and the measured value of the non-contact distance measurement in real time, and forming three corresponding curves S x-Δp 、S x-αβγ 、S x-pnc ；
Step 4, for the S x-Δp Curve sum S x-αβγ Performing wavelet transformation on the curve, and calculating to obtain an x-axis coordinate position x corresponding to the critical contact state of the ball 103-2 and the plane 106 to be measured based on wavelet and signal correlation criteria C ；
Step 5, finding x c At S x-pnc A set { l } of measurements of the corresponding non-contact distance measurement in the curve pnc (i) I=1, 2, …, n }, solving a local space equation x cos phi+y cos phi+z cos omega=v of the plane to be measured by using a least square method;
step 6, utilizing L, x c -x u 、p nc-u And correcting the omega value by the gamma value obtained in the step 2 on a triangle formed by the reference center point of the light splitting module, the measuring site of the non-contact distance measurement and the contact site of the contact probe 103 to obtain omega s The angle value of the plane to be measured is 90-omega s +γ。
Second embodiment
Regarding a geometrical precision measuring device based on the principle of spectral confocal according to a second embodiment of the present invention, the differences from the first embodiment are explained. Fig. 9 is a schematic diagram showing the structural composition of a geometrical precision measurement device based on the principle of spectral confocal according to a second embodiment of the invention. According to a second embodiment of the proposed measuring device, the present invention comprises a dual-mode gauge head 100, a broad spectrum light source 200, a pinhole member 300, a fiber optic path 400, a spectrum detection module 500, and a signal processing module 600. As shown in fig. 1 and 9: the first and second embodiments have the same structure in three parts of the broad spectrum light source 200, the pinhole member 300, the optical fiber path 400, and the like; the non-contact distance measurement working direction of the dual-mode probe 100 in the second embodiment is the same as the optical axis direction of the dispersive lens group 101, and the axial direction of the contact probe 103 is perpendicular to the optical axis direction of the dispersive lens group 101; the spectrum detection module 500 in the second embodiment uses a plurality of photo detectors 504 to obtain the light spectrum of the reflected light received by the pinhole 402-1, the photo detectors 504 use linear array detectors, and the number of photo detectors 504 is consistent with the number of pinholes 402-1; the logic control circuit of the signal processing module 600 in the second embodiment is configured to control exposure of a plurality of the linear array detectors, and convert the reflected light spectrum collected by the corresponding pinholes into digital information for processing by a digital signal processor.
The second embodiment has advantages over the first embodiment in terms of spectral sampling rate, and is suitable for high-speed motion or other working scenes with high real-time requirements.
The above embodiment is only a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the equivalent substitution or equivalent transformation are within the protection scope of the invention.
Claims (10)
1. The geometrical quantity precise measurement device based on the spectrum confocal principle is characterized by comprising a dual-mode measuring head, a wide-spectrum light source, a pinhole component, an optical fiber light path, a spectrum detection module and a signal processing module:
the dual-mode measuring head comprises a dispersion lens group, a light splitting module, a contact probe, a probe base and a shell; the light splitting module divides the light path into two parts, wherein one part is used for non-contact distance measurement and the other part is used for accurately measuring the contact state between the contact probe and the workpiece;
the wide spectrum light source generates white light, is coupled into the dispersion mirror group through an optical fiber optical path, and is dispersed in two directions through the light splitting module;
The pinhole member includes a plurality of pinholes that enable light of a specific wavelength irradiated and focused on a measurement object to return to the pinholes after being reflected, thereby constituting spectral confocal;
the signal processing module is used for decoupling the spectrum distribution information of the two paths of reflected light and obtaining distance data of non-contact distance measurement and contact state of the contact probe;
the reference center point of the light splitting module, the measuring site of the non-contact distance measurement and the contact site of the contact probe form a triangle with known side length.
2. A geometric sense precision measuring device based on a spectral confocal principle according to claim 1, wherein:
the light splitting module is provided with an independent shell, and the shell is detachably and fixedly connected with each other;
and a certain angle is formed between the light splitting surface of the light splitting module and the optical axis of the dispersion mirror group.
3. A geometrical precision measurement device based on the principle of spectral confocal according to claim 1 or 2, characterized in that:
the contact probe comprises a measuring rod and a ball head; the configuration of the measuring rod comprises a straight shoulder measuring rod and a conical measuring rod;
The ball head is positioned at the measuring end part of the measuring rod, and the fixed end part of the measuring rod is connected with the probe base;
the detachable fixing mode is adopted between the probe base and the contact probe;
the probe base has a flat end surface, the roughness Ra is better than 0.5 micron, and the flatness is better than 0.5 wavelength; the position of the flat end surface is at the working distance of the spectral confocal, and the error is less than one tenth of the range of the spectral confocal distance measurement;
the probe base is connected with the shell of the light splitting module, and when the contact probe contacts a measuring object, micro movement can be generated between the probe base and the shell of the light splitting module;
the measuring rod and the ball head are made of materials with high rigidity, and the measuring rod materials comprise ceramics and tungsten carbide; the ball head material comprises ruby, silicon nitride, zirconia and tungsten carbide.
4. A geometric sense precision measuring device based on a spectral confocal principle according to claim 3, wherein:
the optical fiber path comprises a first optical fiber, a second optical fiber, a third optical fiber and an optical fiber coupler, and the end part of the second optical fiber is a pinhole;
the optical fiber coupler is provided with three ports, namely an optical inlet, an optical outlet and a coupling port; one end of the first optical fiber is connected to the wide spectrum light source, and the other end of the first optical fiber is connected to the light inlet of the optical fiber coupler; one end of the second optical fiber is connected to the coupling port of the optical fiber coupler, and the other end of the second optical fiber is connected to the dual-mode measuring head; one end of the third optical fiber is connected to the light outlet of the optical fiber coupler, and the other end of the third optical fiber is connected to the spectrum detection module; the composite light generated by the wide-spectrum light source enters the dual-mode measuring head through the first optical fiber, the optical fiber coupler and the second optical fiber in sequence, and irradiates the light splitting module through the dispersive lens group.
5. The geometrical precision measurement device based on the spectral confocal principle according to claim 4, wherein:
the device comprises a plurality of optical fiber paths, wherein a plurality of second optical fibers form a pinhole component; the pinhole member having pinholes in a number consistent with the number of second optical fibers; the pinholes are distributed at different positions of an image space focal plane of the dispersive lens group; light coupled into the second optical fiber is emitted through the pinhole and subjected to axial dispersion after passing through the dispersion lens group, and light with different wavelengths is focused at different axial positions; light emitted by different pinholes and passing through the dispersive lens group is focused at different object focal plane positions; three or more pinholes are present, and any three of the pinholes are not collinear in spatial distribution.
6. The geometrical precision measurement device based on the spectral confocal principle according to claim 5, wherein:
after light emitted by different pinholes passes through the dispersive lens group and the light splitting module, light with specific wavelength is focused on different positions of the flat end face of the probe base; light with specific wavelength passes through the light splitting module, the dispersion lens group, the pinhole, the second optical fiber, the optical fiber coupler and the third optical fiber in sequence after being reflected by the flat end surface, and finally enters the spectrum detection module; the spectrum detection module acquires spectrum distribution information of the light reflected by the flat end surface and obtains a distance value corresponding to the focusing position.
7. The geometrical precision measurement device based on the spectral confocal principle according to claim 6, wherein:
establishing a measurement space coordinate system by taking the mechanical structure of the dual-mode measuring head as a reference;
taking the optical axis direction of the dispersive lens group as the z direction of the measurement space coordinate system;
taking an object focal plane of monochromatic laser with a specific wavelength as a zero plane in the z direction of the measurement space coordinate system;
the intersection line of the light-splitting surface of the light-splitting module and the zero plane is used as the y direction of the measurement space coordinate system, and the direction perpendicular to the y direction of the zero plane is used as the x direction of the measurement space coordinate system;
the intersection point of the optical axis of the dispersion lens group and the zero plane is the geometric zero point of the measurement space coordinate system, and the direction away from the dispersion lens group is the positive direction of the z axis;
the focusing point of the pinhole corresponding to the flat end surface is marked as P 1 ,P 2 ,…,P n ，P i The coordinates corresponding to the points are noted as (x i ,y i ,z i ) Where i=1, 2, …, n; the space equation of the flat end face is expressed as xcoα+ycosβ+zcosγ=p, and then
Wherein alpha, beta and gamma are respectively included angles between the normal direction of the flat end surface and x, y and z directions of a measurement space coordinate system, and p is the distance from the origin of coordinates of the measurement space coordinate system to the flat end surface;
The distance between the center point of the flat end surface and the center of the ball head is L, the coordinates of the center of the ball head are (L cos alpha-M cos alpha, L cos beta-M cos beta, L cos gamma-M cos gamma+M-delta p),
wherein m=n+Δp, M represents a distance between a specific point on the axis of the touch probe and the origin of the measurement space coordinate system, the specific point having a space coordinate of (0, M), N represents a distance between the center point of the flat end surface and the specific point when the touch probe is not in contact with any measurement object, Δp represents a correction amount of a contact force that causes the center point of the flat end surface to shift in the axis direction of the touch probe, Δp may be calculated iteratively from a space equation according to the flat end surface, and an initial value thereof is Δp=mcos γ -N-p;
and calculating the stress balance of the contact probe by using delta p, alpha, beta and gamma according to the connection mode between the probe base and the shell of the light splitting module, and deducing the contact position and the contact force direction of the ball head.
8. The geometrical precise measurement device based on the spectral confocal principle according to claim 7, wherein the device performs critical contact state position detection by a contact probe, and the detection method comprises the following steps:
Step 1, along a specific direction L k Performing protection movement on a target to be detected, wherein k=x, y and z; when meeting the condition |alpha-90|+|beta-90|+|gamma|not less than T d Or Δp.gtoreq.T p When the movement is stopped, the current L is recorded k Corresponding coordinate position l u-k ；
Step 2, along a specific direction L k Reverse low-speed movement, real-time recording and L k Δp, |alpha-90|+|beta-90|+|gamma| corresponding to the coordinate positions, and two corresponding curves S are formed l-Δp 、S l-αβγ ；
Step 3, curve S l-Δp Sum curve s l-αβγ Performing wavelet transformation, and calculating to obtain L corresponding to critical contact state of ball head and target to be detected based on wavelet and signal correlation criterion k Axis coordinate position l c-k 。
9. The geometrical precise measurement device based on the spectral confocal principle according to claim 7, wherein the device can measure the distance in two directions simultaneously, and comprises the following steps:
step 1, respectively defining two surfaces to be measured as Pn according to a measurement space coordinate system x And Pn z The gesture of the dual-mode measuring head is adjusted to ensure that the x direction of a measurement space coordinate system and the Pn of the surface to be measured are measured x The angle between the normals of (a) is smaller than the maximum allowable angle for non-contact distance measurement;
step 2, measuring the x-axis to-be-measured surface Pn of the space coordinate system x Performing protection movement, analyzing the spectrum obtained by the spectrum detection module, stopping movement when the amplitude corresponding to the 650nm wavelength exceeds a set threshold value, and recording the x-axis coordinate position l nc-x ；
Step 3, measuring the z-axis to-be-measured surface Pn of the space coordinate system z Performing protection movement to obtain a ball head and a surface Pn to be tested z Z-axis coordinate position l corresponding to critical contact state of (2) c-z ；
Step 4, moving to a z-axis coordinate position l along the z-axis of the measurement space coordinate system c-z Analyzing the spectrum obtained by the spectrum detection module; the obtained spectrum has two spectrum peaks, wherein one spectrum peak is with the wavelength of 650nm, and the p value in a space equation of the flat end face is obtained through calculation; another spectral peak corresponds to the measured value n of the non-contact distance measurement, and the surface Pn to be measured is x Distance measurement value l nc-x +n, the surface Pn to be measured y Distance measurement value l c-z +p+L。
10. The geometrical precise measurement device based on the spectral confocal principle according to claim 7, wherein the device can precisely measure the plane angle, and the specific measurement method comprises the following steps:
step 1, selecting a contact probe with a corresponding length according to the range of a plane angle to be measured, wherein the selection principle is that a measurement site A for non-contact distance measurement, a contact site B of the contact probe and a reference center point C of a light-splitting module form an included angle ACB, and the relative error of the plane angle is less than 5%;
step 2, carrying out protection movement along the x-axis direction to the plane to be tested, when |alpha-90|+|beta-90|+|gamma|is not less than T d Or Δp.gtoreq.T p When the movement is stopped, the current x-axis coordinate position x is recorded u And a measurement value p of non-contact distance measurement nc-u The spatial equation xcos α+ycos β+zcos γ=p for the flat end face is recorded simultaneously;
step 3, reversely moving along the x-axis at a low speed, recording the measured values of Δp, |alpha-90|+beta-90|+|gamma| and non-contact distance measurement corresponding to the coordinate position of the x-axis in real time, and forming three corresponding curves S x-Δp 、S x-αβγ 、S x-pnc ；
Step 4, for S x-Δp Curve sum S x-αβγ Performing wavelet transformation on the curve, and calculating to obtain an x-axis coordinate position x corresponding to the critical contact state of the ball head and the plane to be measured based on wavelet and signal correlation criteria c ；
Step 5, finding x c At S x-pnc Measurement value set { l } of corresponding non-contact distance measurement in curve pnc (i) I=1, 2, …, n }, solving a local space equation of the plane to be measured by using a least square method
Step 6, utilizing L, x c -x u 、p nc-u And 2, correcting the gamma value obtained in the step for obtaining omega by using a triangle formed by the reference center point of the light-splitting module, the measuring site for non-contact distance measurement and the contact site of the contact probe s The angle value of the plane to be measured is 90-omega s +γ。
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